Science Musings Blog

Thursday, July 29, 2010

Getting there

Many people keep books or magazines by their toilet, to bide the time while they are sitting on the can. I keep a daddy-long-legs. Or a mommy-long-legs.

A common "cellar" spider, Pholcus phalangioides. They love to winter here in my studio, and when I arrive I generally sweep dozens out with a broom. But I keep a few -- one here under the shelf over my desk, and one in the loo. They are endlessly interesting to watch, although they don't do much but sit there in their almost invisible webs and hope something falls on their plate. Whatever mating they do is done with some discretion -- they like to do it in the dark -- and I suppose my broom makes rather a dint in available partners. But when the tiny baby spiders are born it's all rather exciting, and I feel the proud parent.

Touch the web with a pencil point and they do a dervish dance, some reflex ingrained in deep time, possibly to further entangle a prey in the web, or to make the spider invisible, or to scare away a predator. I don't scare, but I like to see them dance. Imagine that tiny brain controlling those sprawling legs with the skateboarder knee pads.

Here's a mystery. In these climes, at least, Pholcus phalangioides is never found outdoors, or so I'm reliably told by a guidebook. How then do they colonize new barns, cellars, and homes? When we built our cottage it was a quarter-mile from other buildings of any sort, and yet it soon had its population of Pholcus phalangioides. Did they "balloon" here? Some spiders let out a thread that catches the wind and if the thread is long enough the spider can let go of its perch and sail away. It would seem a rather catch-as-catch-can way of finding new indoor spaces to inhabit, but here is this mommy-long-legs, watching me on the can as I watch her. If a reader knows of an answer to this mystery, I'd like to hear it. Surely some arachnidologist has made it her life's work to illuminate Pholcus phalangioides migration. The Book of Job had it long ago: "Ask now the beasts, and they shall teach thee; and the fowls of the air, and they shall tell thee."